From texts to maps to social media, we use our smartphones constantly. And while you may think it’s just a sign of the times, a new study says it may actually be a sign of depression.

According to researchers from Northwestern University, smartphone sensor data can detect depression by tracking the amount of minutes a person uses their phone per day, as well as how often they change their geographical location.

“With phone sensor and GPS data, we can detect if a person has depressive symptoms and the severity of those symptoms without asking them any questions,” said senior study author David Mohr from Northwestern University’s Feinberg School of Medicine.

The study, published in the Journal of Medical Internet Research on Wednesday, involved analyzing the GPS locations and phone usage of 28 people over two weeks. Their locations were tracked every five minutes.

The findings showed that the average daily usage for depressed people is 68 minutes, compared to just 17 minutes for non-depressed individuals.

The data did not reveal how the participants were using their phones, but Mohr says it is likely they were surfing the web or playing games, rather than talking to friends.

“People are likely, when on their phones, to avoid thinking about things that are troubling, painful feelings or difficult relationships,” Mohr said. “It’s an avoidance behavior we see in depression.”

In addition, the researchers found that those who lack a regular day-to-day schedule are at higher risk for depression, as well as those who spend most of their time at home or spend their time in just a few locations.

“The data showing depressed people tended not to go many places reflects the loss of motivation seen in depression,” senior author David Mohr, director of the Center for Behavioral Intervention Technologies at Northwestern University Feinberg School of Medicine, said in a press release. “When people are depressed, they tend to withdraw and don’t have the motivation or energy to go out and do things.”

Participants in the two-week study initially took a standardized questionnaire measuring levels of depression. The PHQ-9 survey asks about symptoms used to diagnose depression – including sadness, loss of pleasure, hopelessness, disturbances in sleep and appetite, and difficulty concentrating. Of the 28 participants, 14 did not have any signs of depression and 14 had symptoms ranging from mild to severe depression.

Once the surveys were completed, lead author Sohrob Saeb – a postdoctoral fellow and computer scientist in preventive medicine at Feinberg – developed algorithms using GPS and phone usage data collected from the phones, and correlated those with the subjects’ depression test results.

The research data could be used in the future to monitor people who are at risk of depression, or offer interventions for people whose smartphones detect it.

“We will see if we can reduce symptoms of depression by encouraging people to visit more locations throughout the day, have a more regular routine, spend more time in a variety of places or reduce mobile phone use,” Saeb said.

Northwestern says it will be conducting future research to examine whether people’s moods are improved when they modify behaviors that are linked to depression.